"Let us follow a corpuscle on its journey"
When Professor Wagstaff (Groucho) is giving a lecture in the classroom, he looks at a large diagram of the internal human body and says "Let us follow a corpuscle on its journey". Then he quickly puts on a hat and picks up a suitcase and starts walking away, then says "Oh my mistake, I thought I was the corpuscle".
I never got the joke. Does anyone know what it's supposed to mean?